Abstract
The influence of alkali cations on mix design of geopolymers is essential for their mechanical, thermal, and electrical performance. This research investigated the influence of alkali cation type on microscale characteristics and mechanical, dielectric, and thermal properties of fly ash-based geopolymer matrices. The geopolymers were elaborated via class F fly ash from the thermal plant Jorf Lasfar, El Jadida (Morocco), and several alkaline solutions. Morphological, structural, mechanical, dielectric, and thermal characteristics of materials synthesized via fly ash with different proportions of KOH and NaOH aged 28 days were evaluated. The physicochemical properties of class F fly ash-based geopolymers were assessed using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDX) analyses. Based on readings of the results obtained, XRD and FTIR analysis detected the creation of semicrystalline potassium/sodium aluminate-silicate hydrate (KASH/NASH) gel in the elaborated matrices after the geopolymerization reaction. The SEM analysis proved the formation of alkali alumina-silicate hydrate gel in the raw material particles after the polycondensation stage. Experimental compressive strength data indicated that the highest compressive strength (39 MPa) was produced by the alkaline activator (75% KOH/25% NaOH). The dielectric parameters values of the elaborated materials changed depending of the mass ratios KOH/NaOH. Dielectric findings demonstrated that geopolymers containing 100% NaOH have better dielectric performances. The fire resistance study revealed that the geopolymer binders induced by KOH are stable up to 600°C. Based on these results, it can be deduced that the formulated geopolymer concrete possesses good mechanical, dielectric, and fire resistance properties.
Highlights
IntroductionOrdinary Portland Cement (OPC) is one of the most commonly applied building materials in the world [1, 2]. e annual global production of this material has increased to 2.8 billion tons and has been estimated to increase to 4 billion tons per year in 2050 [3]
Nowadays, Ordinary Portland Cement (OPC) is one of the most commonly applied building materials in the world [1, 2]. e annual global production of this material has increased to 2.8 billion tons and has been estimated to increase to 4 billion tons per year in 2050 [3].e price and availability of feedstock, the considerable demand for energy, and CO2 emissions are significant preoccupations for the OPC industries
E term geopolymer or inorganic silicate-aluminate material was coined by Joseph Davidovits in 1979 [19]. e geopolymer matrix is an amorphous inorganic polymer elaborated using the polycondensation reaction of aluminosilicate source materials with highly alkaline or acidic activator mediums at room temperature or with a low temperature (
Summary
Ordinary Portland Cement (OPC) is one of the most commonly applied building materials in the world [1, 2]. e annual global production of this material has increased to 2.8 billion tons and has been estimated to increase to 4 billion tons per year in 2050 [3]. E mechanical, thermal, durability, microstructural, and dielectric performances of inorganic polymers or geopolymers were highly influenced by the type of raw materials [31], hydroxide concentration [32], alkaline solution type [26], Si/Al [23], SiO2/Na2O, Al2O3/ Na2O ratios, maturation time [33], temperature curing [34], and so on. Erefore, these previous studies developed the concept for formulation of geopolymer binders by different aluminosilicate precursors and alkaline activators and evaluation of the physicochemical properties of these materials. In this connection, the main aim of the present paper is to compare the impact of potassium and sodium-based activators on the morphological and compressive strength and dielectric and thermal properties of class F fly ash-based geopolymers. The main aim of the present paper is to compare the impact of potassium and sodium-based activators on the morphological and compressive strength and dielectric and thermal properties of class F fly ash-based geopolymers. e effect of alkaline solutions ratio used for producing fly ash-based geopolymers has been examined by means XRD, FTIR, and SEM/EDX. e properties of the produced materials by fly ash and different alkaline activators ratios are investigated and discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
